1. Technical Field
The present invention relates generally to silicon-containing polymers, negative type resist compositions comprising the same, and a patterning method for semiconductor devices using the same. More particularly, the present invention relates to silicon-containing polymers for use in a bi-layer resist (BLR) process, negative type resist compositions comprising the same, and a patterning method for semiconductor devices using the same.
2. Discussion of the Related Art
As semiconductor devices become more highly integrated and complex, the ability to form ultra-fine patterns becomes more important. For instance, in semiconductor devices of 1-Gigabit or greater, a pattern size having a design rule of 0.2 μm or less is needed. Such pattern size is difficult to achieve using conventional lithography processes using lower wavelength devices, e.g., a KrF eximer laser (248 nm), with a conventional resist material. Lithography processes using different exposure light sources, e.g., ArF excimer laser (193 nm) or F2 excimer laser (157 nm), have been proposed.
Further, conventional ArF or F2 resist materials suffer from a variety of drawbacks due to their structural limitation. One problem is the increase in the occurrence of patterns collapsing as the aspect ratio of pattern features increases. Another problem is the weak resistance against a dry etching process. Accordingly, there is an increasing demand for the development of new resist materials and processes.
In photolithography for the manufacture of highly integrated semiconductor devices, a single layer resist (SLR) process and a bi-layer resist (BLR) process are widely used. Use of the BLR process overcomes problems associated with the SLR process. For example, the BLR process increases the resistance to dry etching. Therefore, patterns having large aspect ratios can be formed using the BLR process and high resolution power can be provided at short-wavelength regions.
Generally, a BLR process requires a two component chemically amplified resist comprising a silicon-containing polymer having a silicon atom substituted in the backbone of the polymer and a photoacid generator (PAG), which is a positive type chemically amplified resist. Also, high-sensitivity resist materials suitable for the BLR process developed to be compatible with short-wavelength light sources are mostly positive type chemically amplified resists.
Although positive type chemically amplified resists are preferred in view of their higher resolution, compositions synthesized from the positive type chemically amplified resists suitable for the BLR process are too hydrophobic. Thus, adhesion to underlying layer materials is weak, and it is difficult to control the amount of silicon needed to create suitable resist materials. In particular, the most serious problem with the positive type chemically amplified resists is shrinkage by e-beam. In other words, while observing sizes of resist patterns using a scanning electron microscope (SEM), critical dimensions (CDs) of the patterns may change.
In pursuit of high-speed, highly-efficient DRAMs, there is a limitation in using positive type resists for forming isolated patterns. In lithography processes for the manufacture of semiconductor devices having a memory capacity of 1-Gigabit or more, use of phase shift masks is needed. In the design of phase shift masks, negative type resists are preferred over positive type resists.
Therefore, there is a need to develop negative type resists having a high transmittance to short-wavelength exposure light sources, high resolution power, and high dry etching resistance.